Fix #34 by making the image path relative to the css path
Converted the image input from command line argument to stdin input

This change allows working around the limitted since a spawned command has. (See #33)
Merge pull request #35 from LaurentGoderre/fix-34

Fix #34 by making the image path relative to the css path
Merge pull request #36 from LaurentGoderre/fix-33

Converted the image input from command line argument to stdin input
Merge branch 'master'
typo